Proximity grating microscopy

Structured illumination microscopy (SIM) using grating excitation can be used to extend the bandwidth of fluorescent microscopy by approximately a factor of 2 in the linear regime. If some of the fluorescent molecules are saturated even greater improvements in resolution are possible; this may, however, lead to high levels of photobleaching and phototoxicity. In this paper we present preliminary results that show a simple grating structure separated by a propagation region (see figure 1) can improve the resolution by a far greater factor than this offering the opportunity for resolution close to 50nm. Our present results are proof of concept results on relatively low numerical aperture systems. The potential for the higher lateral resolution relies on the fact that (i) the grating structure does not depend on the illumination optics and can thus be finer than possible with a grating formed by illumination through the lens and (ii) the propagation region can be made from a material with high refractive index is possible with immersion oils.